Advanced nuclear reactors being developed include liquid metal nuclear reactors which use liquid sodium, for example, for cooling the reactor core thereof. In order to circulate the liquid sodium through the reactor core, electromagnetic pumps are used which magnetically pump the liquid sodium therethrough.
More specifically, annular linear induction, or electromagnetic, pumps (ALIP) are known which include annular electrical coils and lamination rings which are stacked together on a common longitudinal centerline axis and have an annular duct extending therethrough. Electrical current provided to the coils induces magnetic flux for pumping the liquid metal through the duct. The coils may be arranged in a single tubular configuration conventionally known as a single stator electromagnetic pump, or two groups of coils may be used, with the first group being configured in one tubular configuration as a radially inner stator, and the second group configured in another tubular configuration as a radially outer stator spaced radially outwardly from the inner stator to define a concentric annular flow duct therebetween in which the liquid sodium is propelled linearly through the electromagnetic pump along its longitudinal centerline axis.
Each of the stators includes a considerable number of discrete coils, with each coil having one or more input and output terminals which must be suitably joined to adjacent coils for carrying the electrical current therethrough. In the double stator electromagnetic pump configuration, the coil terminals of the outer stator extend radially outwardly therefrom, and the coil terminals of the inner stator extend radially inwardly therefrom. Coil terminals of axially spaced apart coils in the inner and outer stators are typically electrically joined together by a longitudinally extending connector in the form of a metal bar. The connector typically extends between every fifth or seventh coil in a stator, for example, for electrically joining together the respective coils. The distal ends of the connector may be suitably joined to the coil terminals by either being welded thereto or riveted thereto in conventional practice.
In an exemplary welded joint between a connector end and a corresponding coil terminal, the end and the terminal may be simply butted end-to-side, respectively, and welded on opposite sides of the joint. Conventional welding results in a relatively small area of fusion between the connector end and the terminal which may increase the electrical resistivity at the joint and provide limited structural strength thereof. In an alternate joint, the connector end and the terminal may be conventionally riveted together in a lap joint. However, such a riveted joint also provides limited structural strength and relatively high electrical resistivity between the riveted members.
Furthermore, although the area surrounding the outer coil in a double stator electromagnetic pump typically provides suitable access to the coil terminals and the connector ends for joining them together during the assembly process, a substantially limited amount of space is available in the annulus region radially inwardly of an inner stator of a double stator electromagnetic pump for joining together the connector and the coil terminals. A welded joint requires access from both sides of the connector to make the joint, and riveting also requires suitable access.
Accordingly, an improved stator for an electromagnetic pump is desired in which the joints between the connectors and the coil terminals may be more readily made during the assembly process, and may have reduced electrical resistivity when compared to welded and riveted joints, while also having improved structural strength for obtaining an improved useful lifetime in an environment subject to elevated temperatures and vibrations found in an electromagnetic pump. Furthermore, an improved connector-to-coil-terminal joint is also desirable for an inner stator of a double stator electromagnetic pump having reduced room in which the joints may be made during the assembly process.